Over the past 90 years, anthropogenic degradation of soil caused by alkaline, magnesium-rich dust deposit has presented a serious problem near magnesite processing factories in Jelšava and in Lubeník (Slovakia). The objective of this study was to investigate the chemical and biological soil properties in 14 sampling sites at different distances from factories, and based on the results, to propose further use of affected land. Results revealed that the available Mg 3–68 fold exceeded very high content for texturally medium soils at all grassland sampling sites, and areas close factory contained up to 14.4–17.4 g kg-1. Higher excess of available Mg caused significant increase of soil pH (up to 9.39) and worsened the conditions for the growth of vegetation. As a result, lower stock of newly formed organic matter (0.50–0.96 g kg-1 of labile carbon) with consequently weaker enzymatic activity occurred. Therefore, enrichment by organic matter provides a measure to support the biological activity of soil. The content of monitored heavy metals (Zn, Cu, Pb and Ni) was not related to Mg and did not influence the enzymatic activity of soil. Because alkaline emissions have decreased by 99.8% since 1970, the application of classical measures (mechanical removal of the Mg-rich crust, incorporation of gypsum and manure to the soil), or newer methods (growing of Mg hyper-accumulating plants) can offer more lasting positive effects than those of 50 years ago. This study concluded that Mg-rich, alkaline dust deposition causes long-lasting anthropogenic soil degradation.
Tobacco production and curing is the single most important contributor to soil degradation and deforestation. To minimise the environmental effects of tobacco production, the environmentally friendly, and energy-efficient rocket barns technology was developed. In spite of its energy saving and environmental benefits, the adoption of rocket barns remains low and understudied. This paper assessed farmers perception and factors affecting the adoption of rocket barn technology. Data was collected using in a cross-sectional survey using structured questionnaires were from 242 Flue Cured Virginia (FCV) tobacco farmers in Uganda. Analysed was done using SPSS and STATA software. Results show that the adoption of rocket barn technology was low, at 12%, with farmers. Farmers perceived adopting the rocket barns technology to be risky and costly. Experience, training, distance to wood fuel, access to extension information, and benefits and risk perceptions were the major determinants of adoption of rocket barns technology. Promotion and adoption of rocket barns technology will require concerted sensitization and training of farmers on the environmental benefits of rocket barn technology. Emphasis such efforts should target the relatively young and inexperienced FCV tobacco farmers.
Insect herbivore has great impacts on biogeochemical cycling in forest ecosystem, but experimental tests on the herbivory-decomposability relationship at the inter-specific level are rare. We conducted a 400-day field decomposition experiment in a temperate mixed deciduous forest and measured mass remaining rate, decomposition constant, total loss of carbon (C) and nitrogen (N) of litter leaf with/without obvious damage by chewing insects for different tree species. We found that herbivory effect on initial litter quality (C: N ratio) varied with species, showing a markedly negative effect on M. alba (-5.78%) and positive effect on Q. acutissima (+5.35%). Herbivory damage increased decomposition constant for M. alba and L. formosana with higher special leaf area, but decreased it for D. kaki and Q. acutissima with lower special leaf area. The contrasting effects of insect herbivory on litter decomposition could be attributed to the variability of litter initial quality caused by herbivory. Our finding that herbivore damage showed inter-specific variability in both litter quality and decomposition rate suggests that herbivory induced feedbacks to nutrient cycling and ecosystem function should be estimated at the species level in multi-species mixed deciduous forest.
The effects of forest conversion from natural forest to agricultural system on soil microbial composition still need further study. Especially, impact on soil function after forest conversion is not yet known. In this study, by using metagenomic sequencing as well as 16S and ITS sequencing technology, we evaluated the soil microbial composition, diversity and functions based on a large number of soil samples of tropical rainforest and rubber plantation across the whole island of Hainan, south China. The results showed that (1) forest conversion changed microbial composition from bacterial groups of Proteobacteria to Chloroflexi, and fungal groups from Basidiomycota to Ascomycota. (2) The bacterial alpha diversity, beta diversity as well as the total diversity did not decrease after forest conversion. However, beta diversity of fungal community reduced resulting a net loss of total OTU richness. (3) There was no difference in soil functional compositions and diversity between rubber plantations and rainforest, however, the relative gene abundance of most COG functions, KEGG functions, CAZy functions as well as Antibiotic gene were significantly different between rubber plantation and tropical rainforest. (4) Soil pH and environmental heterogeneity were the main driver for microbial taxonomic composition and gene functional composition. Land use did not result in changes of functional gene composition, but the relative abundance of functional gene. The changed relative abundance gene would alter the ecosystem processes. In conclusion, our results confirmed that land use changes alter the soil microbial community structure and can have profound effects on ecosystem functions and processes.
How soil quality and microbial communities change in conjunction with stand age in plantations is poorly understood. Here, we evaluated soil quality by using an integrated soil quality index (SQI) and traced the paralleled shifts in fungal community composition by high-throughput sequencing in a chronosequence of Chinese fir (Cunninghamia lanceolata) plantations (stand age of 3, 16, 25, 32, >80 years). Soil properties showed pronounced changes with stand age in the top 0-5 cm. The most prominent increase from 3 to >80-year-old stand was for soil organic carbon (SOC, by 2.1-times), total nitrogen (TN, 1.9-times) and available phosphorus (AP, 2.2-times). SQI increased logarithmically with stand age, with sharper change seen in the 0-5 cm layer than in the 5-15 cm layer. Mycorrhizal fungi increased in abundance initially in younger stands, but then they were gradually replaced by saprotrophic fungi in older stands due to the increase in litter input, which sustains saprotrophs. The positive correlation between saprotrophic fungi and the key soil quality indicators, such as TN, AP and NH4+, showed that higher soil quality was tightly linked with the enrichment of decomposers. Mycorrhizal taxa, such as orders Sebacinales, Thelephorales and Russulales, were positively correlated with acid phosphatase mobilizing P from organic matter. This suggests that the establishment of mycorrhizal fungi sustains tree productivity in younger stands under low soil quality. We conclude that the increase in soil quality throughout the development of Chinese fir plantations is closely linked with the observed transition of fungal communities from mycorrhizae to saprotrophs.
Knowing which restoration approach provides the best returns on investment for accumulating carbon is essential to foster restoration planning, financing, and implementation. We assessed the recovery of carbon stocks, implementation and land opportunity costs of forests established by natural regeneration and high-diversity native tree plantations. Our study was based on chronosequences (10-60 yr) of 12 naturally regenerating forests, 13 restoration plantations, and 5 reference forests located in Brazil’s Atlantic Forest. Restoration plantations accumulated approximately 50% more above-ground carbon than regenerating forests throughout the chronosequence. When controlling for soil clay content, soil carbon stocks were higher in reference than in restored forests, but they were comparable between plantations and regenerating forests. After 60 years of stand development, recovery of total carbon stocks in both restoration management types reached only half of the average stocks of reference forests. Total cost-effectiveness for carbon accumulation, including both implementation and land opportunity costs, was on average 60% higher for regenerating forests than for plantations (15.1 kgC.US$-1 and 9.4 kgC.US$-1, respectively). Both restoration management types had cost-effectiveness for carbon accumulation markedly lower than the price of carbon credits considered, so some voluntary forest carbon markets are not adequately priced to support restoration derived offsets. Although tree plantations initially had higher rates of carbon storage than regenerating forests, their higher implementation and land opportunity costs make them less cost-effective for carbon farming. Our results further suggest that carbon markets alone have a limited potential to up-scale restoration efforts in Brazil’s Atlantic Forest.
Soil pH is strongly associated with soil biogeochemical cycles and biodiversity in terrestrial ecosystems. GE has been widely adopted as an effective practice to restore degraded grasslands. However, the effect of GE on soil pH is still poorly understood and remains inconclusive. We synthesized data from 63 sites in the literature and 43 additional field sites and investigated the dynamics of soil pH following GE across China’s grasslands. Mean pH decreased 0.13 units with GE (mean pH was 8.15 and 8.02 for grazed and GE groups, respectively, p < 0.001). The pH of surface soil (0–20 cm) showed greatest decrease rates in GE grasslands, whereas that of deep soil (20–100 cm) had limited responses to GE. In general, the largest decrease in the rates of soil pH occurred after medium-term periods (5–15 years) of GE, whereas a smaller rate of change was found over short- (≤5 years) and long-term periods (≥15 years) of GE. Of the factors examined, the rate of soil pH change was negatively correlated to MAP, but had no significant relationship with MAT. The rate of soil pH change decreased linearly with RCC, RNC, RAC and RBC. Sedge-dominated grassland had higher pH decrease rates at 0–10 cm soil depth than grass-dominated grassland, whereas grassland dominated by forbs and shrub species showed the highest decrease in pH at 20–30 cm. Our results indicate that GE causes significant soil acidification, especially in surface soil and humid areas, which provides an important reference for future management of China’s grasslands.
Efforts to tackle land degradation worldwide have spurred the adoption of soil and water conservation (SWC) practices intended to reduce surface runoff and erosion. Despite their widespread implementation, missing or incomplete monitoring remains a pervasive problem preventing evaluation of how well SWC practices meet these aims. Key metrics to evaluate SWC efficacy are the production of flow per unit rainfall (runoff ratio), and exported sediment (sediment concentration). We develop a method to assess changes in these metrics in the absence of a flow rating curve, using more complete and reliable measurements of stage (flow depth). We apply these methods to incomplete monitoring datasets collected from five watersheds included in the Tana and Beles Integrated Water Resource Development Project (TBIWRDP) in the Abay (Blue Nile) basin, Ethiopia. Changes in runoff ratio and sediment concentration relative to the first year of treatment varied by season. In the long wet season (Kiremt) that generates most runoff and erosion, reductions in runoff ratio occurred in three watersheds, and reductions in sediment concentration in four watersheds. Reductions in the runoff ratio were directly proportional to the areal density of SWC treatments in the watersheds, suggesting that SWC treatments were effective in controlling runoff and erosion. We suggest that stage and sediment concentration information can be used to assess watershed responses to SWC treatments. Focusing on these relatively robust measurements, may facilitate the design of reliable and affordable monitoring programs, and ultimately facilitate improved financing approaches based on reasonable estimates of likely SWC practice performance.
Bosnia and Herzegovina (BIH) is developing country facing extensive land degradation. As a post-conflict society with underlying poor socio-economic conditions, the value of land and its degradation status are not perceived to be an important problem neither a priority to address. BIH currently exists as a decentralized state, where land and land resources are under exclusive jurisdiction of two entities and one district, rather than state-level legislation. Complex land related administration between entities functioning independently from each other, and thus not sinchronized, leads to frequent political conflicts about land property, and limited data exchange which may exacerbate current land degradation. This paper investigates (i) the institutional setting and policy framework related to land, discussing the effectiveness and limitations of the current policies in this post-conflict society; (ii) stakeholders’ perception of land degradation under such complex institutional and policy structures; and (iii) the current state of land degradation, with a focus on soil erosion as one of the most important indicators in BIH. Communication and cooperation are major challenges for sustainable land management in post conflict societies. The existence of a policy framework is important, but not sufficient if implementation is weak and the perception of decision makers differs. Limited data on the impact of 1992 War on soil and land status represents an additional challenge to combat land degradation. Reliable national data on land degradation are crucial for assessment and development of strategic and policy frameworks devoted to those issues and to raise awareness on how to foster their implementation.
Soil clay content is one of the primary intrinsic soil properties affecting soil erodibility, but few studies have tested the effects of clay amendment on soil wind erosion. The objective of this study was therefore to evaluate the effect of progressive clay amendment on soil wind erosion in the inland Pacific Northwest (iPNW), where there is a high soil erodibility risk due to the arid and semi-arid environment. Clay amendment significantly increased crust crushing energy when physical soil crusts formed after simulated rainfall. Crusts were then subject to simulated tillage to create an erodible soil surface before determining wind erosion in a wind tunnel. Soil loss significantly decreased with increasing clay amendment, even for low clay amendments (2%). In addition, the rate of change in erosion decreased with increasing amounts of clay amendment. Clay amendment was more effective in decreasing soil loss for two sandy loams or soil types with lower clay content. Clay amendment decreased soil loss primarily due to its impact on increasing aggregate geometric mean diameter (GMD), but aggregate crushing energy is also important in decreasing soil loss in terms of decreasing abrasion flux. Clay amendment is thus an effective way to restrain land deterioration in terms of increasing crust crushing energy, aggregate GMD, and decreasing abrasion flux.
Extreme droughts of increased frequency due to climate change poses great challenges to the sustainability of plantations in drylands worldwide. Millions of plantations on China’s Loess Plateau which are mainly in drylands are threatened by serious degradation due to water scarcity. Here we aim to disentangle the impacts of combinations of terracing and mulching on water use strategy and its response to extreme droughts in a rainfed jujube (Ziziphus jujuba) plantation on the semiarid Loess Plateau, using three-year in situ field observations. Pruned jujube branches and maize straw were mulched on half-moon terraces to form two combined treatments, referred to as JBT and MST, respectively. The efficacy of these two combinations on the water use strategy of jujube trees was compared with terracing alone (SHT) and control (no terrace). We found that extreme drought clearly reduced soil water storage (SWS) under all treatments. However, the combined treatments showed significantly (P<0.05) higher SWS than the SHT and control. Furthermore, the combined treatments enhanced soil water use in deep layers during both normal and drought years, thus helping jujube trees to resist droughts. Moreover, the extreme drought significantly reduced transpiration whereas the moderate drought increased transpiration at both seasonal and annual scales. Nonetheless, the combined treatments were associated with enhanced transpiration compared to the SHT and control during drought periods. Finally, jujube trees exhibited isohydric behavior which also helped them to cope with prolonged droughts. Overall, the findings here may provide insights into land management of dryland plantations worldwide under climate change.
Satellite-based solar-induced chlorophyll fluorescence (SIF) has the potential for an early detection and accurate impact assessment of meteorological drought on vegetation photosynthesis. However, how the response of satellite SIF to meteorological drought varies under different climatic conditions and biome types remains poorly understood. In this study, we determined the drought time-scale at which the vegetation photosynthesis response was highest based on the standardized precipitation evapotranspiration index (SPEI) and satellite SIF, and examined how the sensitivity of SIF signals from different ecosystems to drought varied along an aridity gradient in northern China. The results showed that spatial variability of the annual maximum SIF was constrained by wetness conditions and biome types. Annual maximum SIF was positively correlated with SPEI in 57.9% of vegetated lands (P < 0.05). 34.8% of humid ecosystems were characterized by a significant SIF-SPEI correlation (P < 0.05). This percentage reached 44%, 71.4% and 86.2% for arid, sub-humid and semi-arid ecosystems, respectively. The variation of SIF-SPEI correlations was a Gaussian function of the aridity index (AI), with the highest SIF-SPEI correlation appearing in the AI bin of 0.4 (0.37-0.46). The drivers for this pattern were vegetation composition and water availability. The variation of SIF time-scales in response to SPEI was a linear function of the AI, but the slope varied among biomes. To summarize with increasing aridity drought-induced declines in vegetation photosynthesis will be quicker and more significant.
Stopping land degradation is one of the biggest challenges worldwide and particularly in Burundi, which currently faces unprecedented rates of soil loss and food insecurity. This paper proposes a different development discourse on how to stop land degradation, and presents results and lessons learned of a bottom-up inclusive approach implemented since 2014 in Burundi: the Integrated Farm Planning approach (PIP) approach. This approach aims to build a solid foundation for sustainable change towards enhanced food production and good land stewardship, based on three foundation principles (motivation, stewardship and resilience) and three guiding principles (empowerment, integration and collaboration). Findings from an impact study on the PIP approach and testimonies of farmers from a qualitative study show profound changes in land management practices and diversity of activities on the farm, as well as in the social cohesion in households and villages. Based on a vision and a plan, nearly 80,000 motivated households are currently actively involved to stop land degradation and make their farms more productive, while in all PIP villages concrete collective action is undertaken for sustainable land stewardship. Given that these actions are widespread and come along with a change in mind-set rooted in all three foundation principles, the paper concludes that the PIP approach is able to effectively build a foundation for sustainable change. Five key lessons from this experience reveal the key elements of a different development discourse that actually motivates and mobilises farmers to stop land degradation.
Soil salinization is a serious restrictive factor of sustainable agricultural development, and its monitoring accuracy is mainly influenced by such factors as mineral composition, organic matter, and Fractional Vegetation Cover (FVC). Previous research mostly focused on the first two factors and the study of FVC is scarce and unsystematic. In order to systematically explore the effect of FVC, we monitored the soil salinization with different vegetation coverage in Jiefangzha Irrigation District in Inner Mongolia using satellite remote sensing. From May to August 2018, we carried out field sampling at different depths (0-20cm, 0-40cm, 0-60cm) in each month, and calculated FVC and spectral covariates using GF-1 satellite images in the corresponding sampling period. Based on the FVC division criteria of Inner Mongolia, we took the following steps: (1) setting up control treatment A (the full data with undivided FVC,TA) and experimental treatment B (bare land, TB), C (mid-low FVC, TC), D (mid FVC, TD) and E (high FVC, TE); (2) conducting the Best Subset Selection (BSS) for all spectral covariates at different depths of each treatment; and (3) constructing the Soil Salt Content (SSC) inversion models by Partial Least Square Regression (PLSR), Cubist, and Extreme Learning Machine (ELM). The results indicated that classifying FVC could improve the stability and predictive ability of the models. The results can provide references for soil salinization prevention and agricultural production in Jiefangzha Irrigation District and other areas with the same vegetation cover.
Microbial biomass (MB) production and turnover strongly affect soil organic carbon (SOC) accumulation. Microbial carbon use efficiency (CUE) and MB turnover in paddy soil were determined using a novel substrate-independent H218O labeling approach and the effect of long-term fertilization with mineral (NPK) or combined (NPK+OM (manure)) amendments in 0-10, 10-20, and 20-30 cm depths were investigated. Long-term fertilization increased microbial C uptake, CUE, and growth rates, and all indexes were the highest in the NPK+OM treatment. The CUE ranged between 0.07 and 0.23 and showed variable behavior with depth: it reduced in the control treatment, indicating that more C was allocated to energy production than biomass growth, and increased in fertilized soils, showing the shift of C usage for biomass growth. The highest CUE was observed at 20-30 cm in NPK and NPK+OM and indicated that microorganisms overcome the nutrient deficiency in deep soil layers by keeping high C uptake rates at a constant CUE. MBC turnover was more rapid in NPK (10-70 d) and NPK+OM (40-65 d) compared to control (80 d) and intensified with the depth. These findings highlight that under long-term fertilization MB turnover can be controlled by CUE. These shifts in the strategies of microorganisms functioning can explain the accumulation of SOC in heavily fertilized paddy soils.
Excessive salts in soil inhibit enzyme activity, decrease microbial growth and constrain biochemical functioning, which could be alleviated by soil management and fertilization. However, the effect of consecutive chemical fertilizer on soil bacterial community structure under saline environment is poorly understood. Here, a field randomized block design under four nitrogen fertilization rates (0, 150, 300, and 450 kg N hm-2 y-1) was conducted on coastal salt-affected Fluvo-aquic soil. Effect of nitrogen fertilization rates on soil properties and bacterial community was characterized using Illumina Miseq sequencing for 16S rRNA gene. Results indicated that consecutive chemical N fertilization accelerated the improvement of soil chemical and microbial properties under the paddy rice - winter wheat rotation. Soil bacterial community well responded to the nitrogen fertilization and community richness and diversity increased with the nitrogen rates. Predominant bacterial phyla belonged to Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria and Planctomycetes, whereas Deltaproteobacteria, Anaerolineae, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Actinobacteria and Planctomycetia were dominant bacterial classes. Increasing nitrogen fertilization resulted in an elevation in the relative abundance of classes Alphaproteobacteria, Gammaproteobacteria, Planctomycetia and Nitrospira, and a decline in Anaerolineae, Acidobacteria_Gp6, Cytophagia, Bacilli and Acidobacteria_Gp10. Clear separations in the bacterial communities at class level were observed under different nitrogen fertilization rates. Community structure of classes Alphaproteobacteria, Planctomycetia and Nitrospira was significantly influenced by potential nitrification rate (PNR), and community structure of class Actinobacteria was significantly influenced by carbon mineralization rate (CMR). The results demonstrated that nitrogen fertilization improved nutrients and metabolic activities to more suitable bacterial microhabitats for saline soil.